"both this translation and the earlier translation...can be considered authoritative."
Let us compare passage 63 of the Persian Hidden Words (PHW) with passage CIV of Gleanings from the Writings of Bahá’u’lláh (GWB).
PHW: O ye peoples of the world! Know, verily, that an unforeseen calamity followeth you, and grievous retribution awaiteth you. Think not that which ye have committed hath been effaced in My sight. By My beauty! All your doings hath My pen graven with open characters upon tablets of chrysolite.
GWB: O ye peoples of the world! Know, verily, that an unforeseen calamity is following you, and that grievous retribution awaiteth you. Think not the deeds ye have committed have been blotted from My sight. By My beauty! All your doings hath My Pen graven with open characters upon tablets of chrysolite.
Interestingly, someone inquired about these differences and the Research Department replied,
http://bahai-library.com/uhj_hidden_words_pupThe underlying Persian text is the same in both cases. Shoghi Effendi revised his own translations from time to time, particularly in the case of the Hidden Words, and the translation found in Gleanings closely matches the version published in the 1929 edition of the Hidden Words. This translation was revised a final time in 1954 by Shoghi Effendi, and this is the version of the Hidden Words found on the Bahá’í Reference Library Web site. While this most recent version contains the final revisions by Shoghi Effendi, both this translation and the earlier translation published in Gleanings can be considered authoritative.